BACKGROUND: This study was performed to compare efficiency of embryonic stem (ES) cell-derived dopaminergic (DA) neurons from E12 mesencephalic neuronal-precursor derived DA neuron, and to assess the value of these neurons as a donor cells to transplant in Parkinson's disease. METHODS: ES cell-derived DA neurons from E12 mesencephalic neuronal-precursor derived DA neuron were transplanted in Parkinsonian rats and analyzed TH immunoreactivity and apomorphin-induced rotation test. RESULTS: Transplanting of ES cell derived DA neurons into the rat striatum caused gradual increase of expression of tyrosine hydroxylase (TH) immunoreactivity 6 weeks after transplant in host striatum. Rotation behavior was gradually on the decrease, 6 weeks after transplant of ES cell derived DA neurons. In case of E12 mesencephalic precursor derived DA neurons, the TH immunoreactivity expressed 6 weeks after transplant in striatum, and the behavioral restoration of DA-mediated motor asymmetry sustained gradually. However, transplanted ES cell derived DA neurons appeared in wide regions among the needle tract with a relatively high density of TH immunoreactivity in comparison to the E12 mesencephalic precursor DA neurons, and graft volume of ES cell derived DA neurons were larger than E12 mesencephalic precursor derived DA neuron. In addition, both cells did not appear cancerous change after transplantation. CONCLUSIONS: These results suggest that ES cell is more efficient than E12 mesencephalic precursor derived dopaminergic neuron and will supply efficient donor cells for transplantation in Parkinson's disease.